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The Lost OP Wiki: Getting the Best Performance From Your GPS
Overview * GPS considerations ** GPS placement ** GPS interference ** Software * Magnetometer interference = Overview = Thispage lists some suggestions and good practices to follow when planning OpenPilot GPSv9 placement on your vehicle. The page also covers software side steps that improve performance. = GPS considerations = GPS placement The GPS should be placed so that the antenna is pointing towards the sky. Preferably, the GPS is above everything in the copter, and placed on top of a pole or holder that is the upper-most part of the vehicle. For the OpenPilot GPSv9, align the arrows on the GPS PCB pointing forward. It should be mounted level with the copter, the same as with the flight controller, but the GPS does not necessarily have to be in the middle of the vehicle. The picture on the right shows a quadcopter that has the OpenPilot Platinum GPSv9 mounted on a pole. The pole is attached to the copter with nylon screws to protect the GPS in case of a crash. The holder itself is 3D printed, so it will not block any signals. GPS interference Any objects at the sides or on top of the GPS can reduce signal quality significantly. However, there are materials, such as plastic, that are transparent to GPS signals, so plastic is a good material for a GPS protection cover. Especially, electrically conductive materials (carbon and some G10) are bad because they block signals and effectively alter the properties of the GPS unit's antenna. If possible, use nylon bolts to secure the GPS to it's holder. Video transmitters, receivers and telemetry transmitters can emit noise in the GPS band and can interfere with the GPS, so place them as far away as possible from the GPS unit. Software After the GPS unit has been properly configured, settings can be left as-is. However, it is a good practice to reset Home Location before flight to get the best possible performance. You can reset it by going to the System tab in GCS, Settings > HomeLocation > Set > False and then click the red Save button in the top part of the view. After the GPS acquires a lock, it will set the home location back to True by itself. First lock with GPS Icon The first lock with the GPS might take a long time...even 30 minutes. Let the vehicle sit outside in the open and gather satellites. Even if a satellite lock is acquired earlier than the 30-minute mark during the first time, you should still wait before flying because the GPS will download almanac data from the satellites, which will allow a more precise lock faster the next time you power it up. Emergency Firmware Recovery If you find you have a problem with the bootloader or firmware on the GPS, please use the procedures on the Bootloader Update page as a guide to restore it. = Magnetometer interference = The nice thing with magnetometer interference is that it can be avoided using pretty much the same practices that help with GPS signal interference. If using the GPSv9 unit with its on-board magnetometer, it should be mounted as far from high current wires as possible. Mounting it on a pole is a good idea. While the GPSv9 allows you a bit more freedom with high current wiring and power distribution board (PDB) use, you should still build your vehicle to be as magnetometer friendly as possible to get the best performance in the various GPS flight modes the Revolution supports. This means at least the following points: * Twist any high current wires and/or braid/plait anything possible. * Twist the battery wires lightly each time you connect a battery, and remember how you twisted them. Flight configuration should be the same as calibration configuration. * If possible, don't use a power distribution board, but rather a twisted wiring loom (octopus harness). It is pretty easy to make by yourself. A PDB, particularly circular designs, can act as a big electric magnet which is very bad for any magnetometer, and may result in the copter being un-flyable when using the EKF (Extended Kalman Filter) calibration.